A review of hundreds of street stops by the New York Police Department last year found that in over one-quarter, officers failed to document the suspicion that prompted them to stop someone for questioning. In most instances, sergeants signed off on the stop-and-frisk paperwork even when the forms filled out by officers omitted required information.

When street stops led to an arrest, officers rarely documented the stop, in violation of Police Department policy. When people were stopped and questioned, but not arrested, the officers involved rarely gave them a “tear-off” receipt — a new practice intended to bring more accountability to the encounters and help repair strained police-community relations from years of excessive stops among blacks and Hispanics.

The findings, and others, come from departmental audits that analyzed several concentrated periods of stop-and-frisk activity last year. They are described in the second report filed by the federal monitor, Peter L. Zimroth, to the judge overseeing several court-imposed changes for the police.

Taken together, they portray a department still struggling to make its routine inquiries of citizens compliant with the Constitution.

The 94-page report filed on Tuesday morning in Federal District Court in Manhattan does not say the Police Department is violating the court’s orders on street stops; that determination will not be made until well into next year. But the latest update by Mr. Zimroth, who was appointed in 2013, finds a department in need of vast improvement and traces the challenges that Police Commissioner William J. Bratton faces in fixing policies that have been drummed into several generations of officers.

“It is apparent from focus group sessions and discussions with individual officers throughout the ranks that many police officers, including supervisors, are not well informed as yet about the changes underway or the reasons for them and, therefore, have yet to internalize them,” Mr. Zimroth wrote in a letter to Judge Analisa Torres filed with his report. “Many appear not to understand what is expected of them.”

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Police Commissioner William J. Bratton at a briefing in October.CreditChang W. Lee/The New York Times

The Police Department said in a statement that the deficiencies cited in the report might reflect sloppy record keeping and not that the stops lacked reasonable suspicion. The department said its efforts on stop-and-frisk tactics were a “work in progress.”

It said the report will help “in addressing training issues as well as in developing the appropriate reporting forms and documentation procedures.”

Mayor Bill de Blasio, at a news conference on Tuesday in Brooklyn about a possible streetcar line, acknowledged a city and a police force in transition and working with the monitor to improve.

“We obviously want good and accurate information,” said Mr. de Blasio, a Democrat, noting that he had not yet read the report. “But that’s also about training all of our officers in how to do that properly.”

While a police culture cannot transform overnight, mistakes by officers, and their mistreatment of civilians in such encounters, fuels the public’s mistrust of law enforcement.

Protesters have seized on the law enforcement excesses, saying they underlie some of the most notorious encounters of the last couple of years, including the deaths of Eric Garner on Staten Island and Freddie Gray in Baltimore, black men who died in police custody. Those who hailed the manslaughter conviction of an officer last week in the 2014 police killing of Akai Gurley, in Brooklyn, credited their fight for increased law enforcement accountability.

Since Mayor de Blasio took office in New York, the number of recorded street stops has continued to decline, to about 24,000 last year from 45,787 in 2014, according to Mr. Zimroth’s letter. Those tallies represent a small fraction of the stop-and-frisk activity logged during the administration of Mayor Michael R. Bloomberg, a political independent, when recorded stops reached a height of 685,000 in 2011, and fell to about 192,000 in 2013, which was Mr. Bloomberg’s last year in office.

Even with recorded stops receding, broad swaths of officers are yet unable to articulate a rationale for the ones they carry out, or for the frisks that often follow, Mr. Zimroth’s report said. The report — citing a departmental audit of nearly 600 stop reports that officers filled out over 90 days last summer, as part of a pilot program — said documentation for the stops, and frisks, was lacking in nearly 30 percent of cases. Similar findings were included in a broader internal audit of officers’ stop reports and logbook entries for encounters in November and December.

More striking is that sergeants given the task of reviewing stop-report forms in many cases failed to note the officers’ deficiencies, or take steps to correct them, the report said, citing the internal audit of the pilot program.

Sergeants are the front-line supervisors in the department. Their leadership is integral in ensuring that the agency’s new policies are carried out, the report said, if the street-stop program is to succeed.

Prioritizing the work of sergeants comes as Mr. Bratton faces increasingly bitter salvos from Edward D. Mullins, the president of the Sergeants Benevolent Association. Last month, Mr. Mullins accused the commissioner of “political pandering” in disciplining a sergeant present for the encounter that led to Mr. Garner’s death in 2014. On Friday, the union leader told his members that the officer’s conviction in the Gurley case meant they should “do as little as possible” from now on “because this crumbling city does not have your back.”

At the same time, the report by Mr. Zimroth said, “supervisors must take a more active role in supervision, oversight, teaching and, when appropriate, discipline.”

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Mayor Bill de Blasio at the Police Academy graduation ceremony in 2014. Since Mr. de Blasio took office, the number of recorded street stops has continued to decline, to about 24,000 last year from 45,787 in 2014, according to a letter from the federal monitor.CreditRichard Perry/The New York Times

Yet, on discipline, the report said many officers were not aware of the revised rules prescribing more instruction and training as remedies for inaccurate or incomplete stop reports. Their fears of being harshly punished for even good-faith mistakes in documenting stops inhibits officers from changing their behavior.

“The system should be seen as legitimate by the police and the community being served,” the report said, echoing a theme by Mr. Bratton to push “precision policing” upon not only the community, but also his officers.

A practical effect is that officers fail to document each stop, which undercuts the department’s quest for accurate measurements, the report noted. The persistent undercounting is exacerbated by uncertainty about the stop-and-frisk law, and how to carry it out equally and reasonably, particularly in the most crime-plagued communities that saw a bulk of the stops deemed legally unjustified.

To help solve many of its problems, the department has offered new training to its recruits and has paired rookie officers with more seasoned trainers. But it has yet to incorporate training on “implicit bias” and “procedural justice” for the entire force of 36,000 officers, who are expected to draw on such knowledge not only for street stops but also in writing summonses, aiding victims and making arrests, the report said.

With instruction at the heart of the department’s efforts, Mr. Zimroth and his team observed “some poor teaching” at the Police Academy, the report said. Teachers need more training, particularly in social psychology, history and the law.

“It was evident from observing lessons delivered by some instructors,” the report said, “that simply providing a lesson plan, student guide and two-week course in methods of instruction on top of their own experiences is not sufficient to deliver quality instruction for officers in the increasingly complex and changing world of 21st century policing.”

Advocates for police reform, and those representing the plaintiffs in the case that led to the court’s ruling, said the report raised concerns, especially about the constitutionality of stops last year that are documented and not.

“This report’s disclosure about police stops shows how much work still needs to be done to put an end to unconstitutional stops,” said Christopher T. Dunn, the associate legal director of the New York Civil Liberties Union, which represented plaintiffs in one case.

A version of this article appears in print on , on Page A20 of the New York edition with the headline: City Police Still Struggle to Follow Stop-and-Frisk Rules, Report Says. Order Reprints | Today’s Paper | Subscribe